A New Flavonol Triglycoside and Other Flavonol Glycosides from Astragalus armatus Willd. (Fabaceae)

From the aerial parts of Astragalus armatus, a new acylated flavonol triglycoside, isorhamnetin-3-O-(5'''-p-hydroxybenzoyl)-beta-apiofuranosyl-(1 -> 2)[alpha-rhamnopyranosyl-(1 -> 6)]-beta-galactopyranoside (1) which we named astrarmatuside, has been isolated and structurally elucidated together with seven known flavonol glycosides: tamarixetin-3-O-alpha-apiofuranosyl-(1 -> 2)[alpha-rhamnopyranosyl-(1 -> 6)]-beta-galactopyranoside (2) (millettiaspecoside D), isorhamnetin-3-O-alpha-apiofuranosyl-(1 -> 2)[alpha-rhamnopyranosyl-(1 -> 6)]-beta-galactopyranoside (3), kaempferol-3-O-alpha-rhamnopyranosyl-(1 -> 2)[alpha-rhamnopyranosyl-(1 -> 6)]-alpha-glucopyranoside (4), kaempferol-3-O-alpha-rhamnopyranosyl-(1 -> 2)[alpha-rhamnopyranosyl-(1 -> 6)]-beta-galactopyranoside (mauritianin) (5), isorhamnetin-3-O-alpha-rhamnopyranosyl-(1 -> 2)[alpha-rhamnopyranosyl-(1 -> 6)]-beta-galactopyranoside (6), kaempferol-3-O-alpha-rhamnopyranosyl-(1 -> 6)]-beta-glucopyranoside (nikotiflorin) (7) and isorhamnetin-3-O-alpha-rhamnopyranosyl(1 -> 6)]-alpha-glucopyranoside (narcissin) (8). The structures of the isolated compounds were established by means of 2D NMR experiments, HPLC-DADMS, HR-MS and UV spectral analyses. Pivotal role in the structure elucidation and in particular in the determination of sugar sequence, played HSQC-TOCSY and ROESY experiments whereas those of the known compounds (2-8) were established by spectral comparison with those published in the literature.